This invention pertains to thermosettable compositions which simultaneously contain both a maleimide group and a cyanate group.
Aromatic polycyanates which are thermosettable to polytriazines are known, for example, from U.S. Pat. Nos. 3,448,079; 3,553,244; 3,694,410; 3,740,348; 3,755,402; 4,094,852 and 4,097,455. Said polytriazines possess excellent heat resistance, however, an improvement in their mechanical properties, especially tensile strength and elongation would be desirable. Furthermore, there is substantial room for improvement in the moisture resistance of said polytriazines.
Polymaleimides which are thermosettable are known, for example, from U.S. Pat. No. 2,444,536 and from New Industrial Polymers, Rudolph D. Deanin (editor), ACS Symposium Series 4 published by American Chemical Society, Washington, D.C. (1972), pages 100-123. Said polymaleimides are typically difficult to process and cure due to high melting points, poor solvent solubility and slow curing rates. The thermoset (cured) polymaleimides are very brittle and thus of limited utility.
Copolymerization products of compounds containing two or more maleimide groups with compounds containing two or more cyanate groups are also known, for example, from Proc. Electr./Electron. Insul. Conf., 1981, 15th, pages 168-171. Representative of said copolymerization products is the bismaleimide-triazine resin prepared by copolymerization of bisphenol A dicyanate and N,N'-(methylenedi-p-phenylene)bismaleimide. Preparation of said copolymerization products always requires premixing or contacting together two separate components: the polycyanate compound and the polyaleimide compound.
The present invention provides novel compositions which simultaneously contain both a maleimide group and a cyanate group. Said compositions are thermosettable to useful polymeric (cured) compositions including castings, laminates, coatings and the like. Many of the compositions of the present invention possess improved mechanical properties and improved moisture resistance when compared to the polytriazines of the prior art. In addition, improved processability is inherent to the compositions of the present invention.